February 2014 Issue

The Mediterranean Diet and Cognition
By Lindsey Getz
Today’s Dietitian
Vol. 16 No. 2 P. 26

Growing evidence suggests that following this eating pattern may improve memory and prevent neurodegenerative disease.

Memory loss often is indicative of the normal aging process, but it also may be a sign of neurodegenerative disease development, namely Alzheimer’s disease, a form of dementia that causes problems with memory, behavior, and thinking, and gradually worsens over time. While there’s no known cure for Alzheimer’s, research suggests that a healthful lifestyle that includes following a Mediterranean pattern of eating and regular physical activity may delay or slow the disease’s progression.

A Healthful Connection
An estimated 5.2 million Americans of all ages have Alzheimer’s, including 5 million people aged 65 and older as well as approximately 200,000 who have younger-onset Alzheimer’s. Experts believe that number will increase to 7.1 million by 2025 and nearly triple by 2050.

“Alzheimer’s is caused by the accumulation of two chemicals in the brain: amyloid and tau,” explains Nikolaos Scarmeas, MD, MSc, an associate professor of neurology at Columbia University Medical Center. “Why they accumulate in abundance is not known, but they negatively affect brain cells that eventually die. Due to the loss of brain cells, the patients with this disease experience cognitive decline. The decline starts from memory because the brain cells responsible for memory are affected first but involves gradually, over the course of about a decade, the decline of all higher cognitive functions.”

Alzheimer’s is the most frequent type of dementia, adds Miguel A. Martínez-González, MD, PhD, MPH, chair of the department of preventive medicine and public health in the medical school at the University of Navarra in Spain. In addition to memory, it impairs the ability to perform activities of daily living and is characterized by a progressive chronic impairment, he says.

The disease can be devastating to patients and their families. Although the reasons aren’t fully understood, there does seem to be a link between a healthful lifestyle and a decrease in cognitive impairment. Recent research has focused more specifically on the positive benefits of the Mediterranean diet and the reduced risk of Alzheimer’s as well as other cognitive functions.

A Mediterranean diet essentially is a plant-based diet that’s characterized by consuming a variety of fresh fruits and vegetables, grains, and plenty of fish. “Modest amounts of olive oil are used instead of butter, and you basically use food to flavor food, such as basil, garlic, and onions,” adds Joan Salge Blake, MS, RD, LDN, a nutrition educator and clinical associate professor at Boston University and a national spokesperson for the Academy of Nutrition and Dietetics (the Academy). “It focuses on using seasonal foods, so it’s a fresh and tasty diet. Meat and sweets are consumed in very small portions, and it’s about making fruits and vegetables the main focus of the plate.”

Past research has indicated that this diet, high in fruits, vegetables, and unsaturated fatty acids, has been associated with slowing and even preventing the metabolic syndrome, protecting the kidneys, and reducing the risk of other chronic diseases such as heart disease and diabetes and, more specifically, neurodegenerative disease. For example, a meta-analysis published in the October 2013 issue of Annals of Neurology showed that high adherence to a healthful dietary pattern, such as the Mediterranean diet, may be beneficial in the prevention of various conditions linked to the aging brain, including cognitive decline, depression, and stroke. The research team behind the meta-analysis, led by Theodora Psaltopoulou, PhD, of the University of Athens School of Medicine in Greece, found that a Mediterranean diet was protective for both of the study’s subgroups, participants who had mild cognitive decline and those who had advanced cognitive decline, and showed positive effects when looking specifically at Alzheimer’s.

Another meta-analysis, published in the July 2013 issue of Epidemiology, also found that greater adherence to a Mediterranean diet was associated with slower cognitive decline and a lower risk of developing Alzheimer’s. The researchers of this meta-analysis suggested that further studies are warranted to clarify a possible association between diet and mild cognitive impairment or vascular dementia, along with long-term randomized controlled trials looking more closely at the possibility of preventing or delaying the onset of Alzheimer’s.

Moreover, according to recent research presented at the Society for Neuroscience meeting in November 2013, there was a significant association with slowed decline in executive function (eg, the ability to remember details, switch focus, manage time and attention) at three years’ follow-up among subjects who adhered to a Mediterranean diet. Those who adhered to a Western diet (rich in red meat, processed foods, refined grains, potatoes, and fatty dairy foods) had a significantly increased risk of declines in visuospatial functioning, the ability to process and interpret visual information about where objects are in space, at three years’ follow-up.

While there’s research suggesting there are many positive benefits associated with following a Mediterranean diet, the reason why this diet may lead to better brain health remains uncertain, although many theories exist. Researchers and dietitians tend to agree that consuming a diet that’s primarily plant based, focused on real and whole foods, and devoid of processed foods and red meat has much to do with its positive effects on cognitive health.

Weighing in on the Research
Proponents of the Mediterranean diet tend to single out the health benefits of olive oil and focus on the omega-3 fatty acids. However, some believe the cognitive benefits may result more from a synergistic combination of all the healthful foods that make up the diet. “It might be the omegas, the antioxidants, the flavonols, and the large number of vitamins all working together to have the positive benefit of reducing cognitive impairment,” says Kathy McManus, MS, RD, LDN, director of the nutrition department at Brigham and Women’s Hospital in Boston. “Or it may just be the fact that those who consume a Mediterranean diet tend to be healthier individuals in the first place.”

Marjorie Nolan Cohn, MS, RD, CDN, ACSM-HFS, a national spokesperson for the Academy, agrees: “When you look at the research, there are many variables that can’t be counted. These are correlational studies that report on what people ate 20 years ago. The fact is that those who followed a Mediterranean-like diet, probably have other healthful habits too, which complicates it even more since other factors, such as physical activity, also may have had a role in preventing Alzheimer’s. But what can’t be discounted is the fact that this is an all-around very healthful diet and regardless of whether you can pinpoint the exact healthful effects it may have, it still makes sense to adopt it.”

While focus often is placed on the foods eaten in any given diet, Sharon Palmer, RD, author of The Plant-Powered Diet, adds that with the Mediterranean diet, it may be as much about what’s not eaten that makes this diet so beneficial. “In a traditional Mediterranean diet, you’re avoiding high amounts of meat, refined carbs, and highly processed foods, and in their place you’re filling up with all the good stuff: minimally processed grains, lots of seasonal and local fruits and vegetables, legumes, olive oil, nuts, and seeds,” she explains. “You’re limiting your saturated fats, high-glycemic carbs, sodium, and cholesterol because you’re not eating a lot of meat and highly processed food. The Mediterranean diet originated from one that was locally available in poor countries. They ate things that surrounded them, and there was no room for industrial, imported foods. It was the ‘poor man’s diet’ in which people made something of nothing—foraging foods, fishing the oceans, and growing their own produce.”

In addition, research on the brain has indicated that chronic inflammation is a factor in Alzheimer’s development, and therefore the anti-inflammatory effects of the Mediterranean diet are surmised to be a possible reason behind improved cognitive function. “Some components present in fruits, vegetables, nuts, red wine, and virgin olive oil are able to exert potent anti-inflammatory effects,” Martínez-González says.

Incorporating the Mediterranean Diet
While the Mediterranean diet has received much attention recently, clients still may not know what it is or how to incorporate it into their daily lives. “One of the things that always surprises me is how often people say they don’t know what it is,” McManus says. “As dietitians, we hear so much about it, but my patients often say they’ve never heard of it, and even if they have, they don’t really understand what it is. So the first step is educating people about what a Mediterranean diet means. The keys are that it’s plant based, it involves whole foods, and it involves real food. I give my patients a copy of the [Mediterranean diet] pyramid, which they find helpful. Oldways [which created the pyramid] also is an excellent source for information.”

The big thing is helping people translate the diet into their own daily lives, Palmer says. “I think a lot of people think of the diet as just using olive oil on everything, but olive oil is just one facet of the diet. At its core, the diet focuses on whole, locally available, seasonal plant foods; healthful fats; and fish as the primary animal protein. So you can take that concept and apply it to a diet in the Midwest, Northwest, or South by asking: what are the locally available whole plant foods in this region? And what fish are available? People need help translating diet patterns to their region.”

Adherence to the diet also means applying it to particular culinary traditions within a person’s lifestyle, Palmer continues: “For example, if you have Scandinavian heritage, you can apply the Mediterranean diet strategy to your own favorite food traditions by eating whole grain rye bread, enjoying traditional fish dishes, and enjoying favorite vegetable dishes such as those based on beets, cabbage, and carrots.”

As your clients and patients begin to adopt practices of the Mediterranean diet, they may find it’s easier to do than they once thought. To help them make a commitment, Nolan Cohn tells patients to choose two days each week for fish dinners and stick with them. Because fish doesn’t have as long a shelf life like other protein products, she suggests that “fish night” be within a day or two of grocery shopping.

While the Mediterranean diet is focused on fish as a main protein source, Nolan Cohn says those who have trouble giving up red meat may be pleased to know that grass-fed lean beef, though often much more expensive than non–grass-fed beef, is high in omega-3 fatty acids and low in fat. “Contradictory to what people have heard for so long about the Mediterranean diet, this is a way that you’re able to make a compromise and get that beef, which can be hard for some to give up,” she says. “It’s more costly, so it might be once a week or a special treat, but many patients appreciate learning it’s not something they have to completely avoid.”

Produce also can be expensive, but for those who are concerned about cost, Salge Blake says that buying what’s in season will be most cost-effective and most tasty, too. “I try to convey how easy it is to cook in the Mediterranean diet,” she notes. “Roasting vegetables is wonderful, and it’s easy. All you need is a little bit of olive oil and some herbs and spices. You can try any combination: shallots and onions with savory chunks of squash, broccoli and garlic, or whatever it is you prefer. The next day the vegetables are even delicious cold or tossed in with a salad.”

Salge Blake says offering patients recipes is one of the best ways to set them up for success. And research seems to indicate that an educated patient is a successful one. Martínez-González says that after 6 1/2 years of follow-up with more than 500 patients in the PREDIMED-NAVARRA randomized trial, the groups who were educated about the Mediterranean diet had significantly better cognitive abilities than those who didn’t receive the education.

The bottom line is that one reason the Mediterranean diet has such health potential is that it’s delicious and easy, and it sets people up for success, according to Palmer: “The diet has evolved over thousands of years in this region of the world. It’s not at all about deprivation. You can have a good percentage of healthful fat—olive oil, avocados, and nuts—which makes everything taste great. And the foods have lots of flavor; they’re fresh and local. Plus it even includes moderate wine [consumption]. It’s about a lifestyle, not a diet. If you go to the Mediterranean, you’ll observe that people don’t think of their eating style as a diet, it’s just the way they live—and they love it.”

— Lindsey Getz is a freelance writer based in Royersford, Pennsylvania.